Inert gas fire suppression systems are being used to replace systems using Halon suppressants because such Halon-based systems are considered to be damaging to the environment. Systems using inert gas are generally required by safety standards to deliver inert gas to a room or other target zone so that the inert gas occupies approximately 40% by volume of the room. This lowers the oxygen level within the room to about 10 to 15%, which starves a fire of oxygen. The safety standards generally require that 95% of the required amount of inert gas is delivered to the protective room within sixty seconds. Preferably, the inert gas is selected so as not to be harmful to any occupants of the room, and may be so selected that the atmosphere in the room is breathable even after deployment of the fire suppressant gas.
In order to provide the desired rate of delivery to the protected room, the inert gas is typically stored in a plurality of containers at very high pressure, such as 200 to 300 bar. Each of these containers is connected to a manifold which supplies the inert gas, when required, to the target room. Such a known arrangement is shown in FIG. 1.
Because the highly pressurised inert gas must be supplied to the target room rapidly, it is necessary to provide the target room with vent areas so as to reduce the peak pressure within the target room and avoid structural damage upon discharge of such high volumes of gas. Also, the manifold and piping from the manifold to the target room must be capable of withstanding the high peak pressure generated when fluid is discharged from each of the plurality of containers simultaneously. Such heavy duty piping is expensive.
WO-A-2004/079678 (Fike Corporation) discloses an inert gas fire suppression system in which the inert gas is stored in a plurality of pressurised containers. Each of the containers is provided with a respective specially designed discharge valve which is said to control the discharge of gas so that it is delivered at a generally constant pressure. The discharge valve has a complex structure, and controls the flow rate of fluid from the pressurised container in dependence upon variations in the pressure of that container.